The Drosophila Tis11 gene appears to be differentially spliced to produce four separate transcripts and two proteins. Essentially nothing is known about the function of this protein in Drosophila, although its transcripts are expressed in all developmental stages from early embryo to the adult. Insertion mutations that seem to eliminate the gene product cause a delay in development, poor viability, and defects in the extremities among the survivors, while over expression may cause early death. Efforts are underway to induce null mutations by deleting one and/or both promoters using imprecise excision of a transposable P element located immediately upstream of the first promoter. Antisera are also being prepared to peptide fragments of the protein.